1. Field of the Invention
This invention relates to an electro-luminescence display (ELD), and more particularly to an organic electro-luminescence display device and a fabricating method thereof that are adaptive for preventing a badness of a pad portion.
2. Description of the Related Art
Recently, there have been developed various flat panel display devices reduced in weight and bulk that is capable of eliminating disadvantages of a cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence (EL) display, etc. Also, there have been actively processed studies for attempting to make a high display quality and a large-dimension screen of the flat panel display device.
In such flat panel display devices, the PDP has drawbacks in that it has been highlighted as the most advantageous display device to make a light weight, a small size and a large dimension screen because its structure and manufacturing process are simple, but it has low light-emission efficiency and large power consumption. On the other hand, the active matrix LCD employing a thin film transistor (TFT) as a switching device has drawbacks in that it is difficult to make a large dimension screen because a semiconductor process is used, and in that it has large power consumption due to a backlight unit and has a large light loss and a narrow viewing angle due to optical devices such as a polarizing filter, a prism sheet, a diffuser and the like.
Meanwhile, the EL display device is largely classified into an inorganic EL display device and an organic EL display device depending upon a material of a light-emitting layer, and is a self-luminous device. When compared with the above-mentioned display devices, the EL display device has advantages of a fast response speed, large light-emission efficiency, a large brightness and a large viewing angle. The inorganic EL display device has a larger power consumption than the organic EL display device, and can not obtain a higher brightness than the organic EL display device and can not emit various colors such as red(R), green(G) and blue(B) colors. On the other hand, the organic EL display device is driven with a low direct current voltage of tens of volts, and has a fast response speed. Also, the organic EL display device can obtain a high brightness, and can emit various colors of red(R), green(G) and blue(B). Thus, the organic EL display device is suitable for a post-generation flat panel display device.
FIG. 1 is a schematic section view showing a structure of a conventional organic EL display device, and FIG. 2 is a section view of the organic EL array taken along the I-I′ line in FIG. 1.
Referring to FIG. 1 and FIG. 2, the organic EL array 50 has a first electrode (or anode electrode) 4 and a second electrode (or cathode electrode) 12 provided on a substrate 2 in a direction crossing each other.
A plurality of first electrodes 4 are formed on the substrate 2 in such a manner to be spaced at a desired distance from each other. An insulating film 6 having an aperture for each EL cell area is formed on the substrate 2 provided with the first electrode 4. On the insulating film 6, a barrier rib 8 for making a separation of an organic light-emitting layer 10 and the second electrode 12 to be formed thereon is positioned. The barrier rib 8 is provided in a direction crossing the first electrode 4, and has an overhang structure in which the upper portion thereof has a larger width than the lower portion thereof. The organic light-emitting layer made from an organic compound and the second electrode 12 are entirely deposited onto the insulating film 6 provided with the barrier rib 8. The organic light-emitting layer 10 expresses red(R), green(G) and blue(B) colors. Generally, the organic light-emitting layer 10 is formed by patterning individual organic materials light-emitting red, green and blue colors for each pixel P.
As shown in FIG. 2, the organic light-emitting layer 10 includes a hole injection layer 10e, a hole carrier layer 10d, a light-emitting layer 10c, an electron carrier layer 10b and an electron injection layer 10a that are sequentially provided on the first electrode 4.
In such an organic EL display device, if a voltage is applied between the first electrode 4 and the second electrode 12, then electrons (or cathodes) generated from the second electrode 12 are moved, via the electron injection layer 10a and the electron carrier layer 10b, into the light-emitting layer 10c. Further, holes (or anodes) generated from the first electrode 4 are moved, via the hole injection layer 10e and the hole carrier layer 10d, into the light-emitting layer 10c. Thus, the light-emitting layer 10c forms exiton by a re-combination of electrons and holes fed from the electron carrier layer 10b and the hole carrier layer 10d. Then, the exiton is again excited into a base state to emit a certain energy of light, via the first electrode 4, into the exterior, thereby displaying a picture.
The organic EL array 50 has a property liable to be deteriorated by moisture and oxygen. In order to overcome this problem, an encapsulation process is carried out. Thus, the substrate 2 provided with the organic EL array 50 is joined to a cap 28 by a sealant 26.
FIG. 3 shows a pad portion of the conventional organic EL display device.
A pad 37 of the pad portion of the organic EL display device shown in FIG. 3 is electrically connected to a signal supplying film 32 such as a chip on film (COF) and a tape carrier package (TCP), etc. with having an anisotropic conductive film 30 therebetween for the purpose of receiving a driving signal from the exterior thereof. The pad 37 has a structure in which a transparent conductive layer 36 connected to the first electrode 4 or the second electrode 12 of the organic EL array 50 and opaque conductive layer 34 are layer-built. Herein, indium-tin-oxide (ITO), indium-zinc-oxide (IZO), indium-tin-zinc-oxide (ITZO) or the like is used as the transparent conductive layer 36 while molybdenum (Mo), etc. is used as the opaque conductive layer 34. Further, a silicon film 38 for preventing an oxidation of the opaque conductive layer 34 caused by moisture and oxygen, etc. is provided on the opaque conductive layer 34.
Meanwhile, the opaque conductive film 34 provided at the pad portion of the conventional organic EL display device is corroded due to moisture (H2O) and oxygen (O2), etc., thereby frequently causing a poor pad problem in that a driving is not applied via the signal supplying film 32.
This will be described in detail below.
Generally, the opaque conductive layer 34 made from molybdenum (Mo), etc. has a property of oxidation or corrosion when it is exposed to moisture and oxygen, etc. Such an opaque conductive layer 34 is exposed to moisture or oxygen in the atmosphere as shown in FIG. 4 in the course of carrying out a joint process of the substrate 2 provided with the organic EL array 50 to the cap 28 and a connection process of the pad 37 to the signal supplying film 32 with having the ACF 30 therebetween, etc. The exposed opaque conductive layer 34 undergoes oxidation. Also, after forming the silicon film 38, oxygen and moisture are permeated into an interface among the silicon film 38, the transparent conductive layer 36 and the opaque conductive layer 34, thereby causing an oxidation of the opaque conductive layer 34. Such an oxidation accelerates an galvanic corrosion resulted from a difference of voltages applied to each pad 37, thereby causing a poor pad portion problem in that an external driving signal is not applied to the organic EL array 50.